Snowmobile ski

ABSTRACT

This invention relates to an improved snowmobile ski having a vertical fin on the topside of the ski with a surface area large enough to minimize or prevent sideways slippage of the ski during a turn. The fin, if a single fin is used, is located adjacent the outboard edge of the ski. A snowmobile ski with dual topside fins having outwardly projecting lips along the upper edges of said fins has improved performance in deep snow.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/177,393,filed Jun. 21, 2002, pending, which will issue Jan. 31, 2006 as U.S.Pat. No. 6,991,056, which is related to application Ser. No. 10/176,172,also filed Jun. 21, 2002, now U.S. Pat. No. 6,955,236, issued Oct. 18,2005.

BACKGROUND OF THE INVENTION

1. Field

This invention relates to snowmobile skis and in particular tosnowmobile skis which are versatile, being useful on ice, hard-packedsnow or in deep, powdery snow.

2. State of the Art

Snowmobile skis have undergone considerable evolution in recent years.Traditionally, metal skis had been utilized for decades until the recentdevelopment of plastic skis. Also, skis have gone from being essentiallyflat to having a curved or rocker shape as illustrated and claimed invarious U.S. Patents to Noble, namely, U.S. Pat. Nos. 5,700,020,6,012,728 and 6,267,392. The latter two patents also introduced theconcept of having a plurality of keels and especially a tri-keel designwherein there is a central longitudinal keel which is deeper than twooutboard keels. The advantage of this triple keel design is that itpermits the skis to be more versatile, giving traditional steeringcontrol on hard surfaces, for example, ice, via the central keel, andthen in deeper snow where the outboard keels take over some of thefunction of the central keel in permitting easy, straight-ahead steeringand providing better control in turns, especially in deeper snow.

U.S. Pat. No. 4,491,333 to Warnke discloses a flat ski with flared flatrunning surface extensions to maximize ski flotation in deep snow. Theseflat wings are an extension of the ski running surface in that themargins of the ski are flared upward at an angle of 30° to 60° to thesnow surface. The patent states that better lift is achieved in turns indeep snow without affecting the characteristics of the skis when run onhard pack snow. The flared ski margins serve to increase the effectivewidth of the skis.

Snowmobiles have a long extended track which tends to cause thesnowmobile to proceed along the longitudinal axis of the track even in aturn. The long track is rapidly moving and it tends to propel thesnowmobile straight ahead even when the skis are turned, thus there is aplowing action of the skis in turns. Skis having some vertical surfacearea such as provided by the three keels militate to some extent againstthe sideways or lateral motion of turned skis. The snowmobile steeringmechanism is structured with a camber so that when the snowmobile skisare turned the skis tilt away from a flat, running aspect. Thestraight-ahead, plowing effect may be pronounced in deep snow at anyspeed where the snow is very powdery and light such as that foundfrequently in the western United States.

BRIEF SUMMARY OF THE INVENTION

The instant invention relates to an improved snowmobile ski which has atleast one outboard, topside fin having a substantially verticalorientation and sufficient vertical area to resist sideways slippage ofthe ski during a turn in deep snow, especially in deep, light, powderysnow. The fin is structured to be sufficiently strong to resist bendingor breaking when the fin is pressing against snow during a turn of theski. The fin generally has a surface area forward of approximately themidpoint of the ski which is approximately equal to the surface area ofthe fin aft of the skis' approximate midpoint. Also, the fin preferablyhas a surface area (sail area) which increases from the forward portionof the ski as it approaches the midportion of the ski and then decreasesas the fin diminishes in height toward the aft end of the ski.

Multi-keel skis, especially those of a rocker design, are particularlysuitable for the inclusion of a fin of the type described herein. Thefin with respect to a rocker shape ski may also have an inverse rockershape so that the surface area of the fin decreases both to the frontand to the rear of the approximate midpoint of the ski.

Because skis do tilt during turns, the fin, if it is substantiallyvertical, which includes being substantially perpendicular to the topsurface of the ski, will tilt so that its top portion is inboard of itsnormal position in a flat, straighthead running position. This inwardtilt of the fin permits snow against which the fin is pressing to slideupwards and slide over the top of the fin. An additional feature of theinvention is to provide a lip along the top edge of the fin which lipprotrudes to the outboard so that as snow slides up the fin during aturn it contacts this overhanging lip and is prevented from sliding upand over the top of the fin thereby giving the fin greater impact for aparticular surface area than it would have without this top-edge lip.

In a preferred construction, the skis have dual topside fins, one finalong each. lateral edge of the ski. Also, a further preferred skistructure is where each such topside fin has an outwardly projecting lipalong a significant portion of the upper edge of each fin, as discussedin more detail hereinafter.

An advantage of having the fin topside of the ski rather than creatingdeep keels beneath the ski to prevent side slippage is that a certainoptimum depth of keel or keels is required to give the ski good handlingunder various kinds of conditions, such as ice or hard pack or slush aswell as deep, heavier snow and deep, powdery snow. Thus, to design asingle keel or multiple keeled ski to be specially constructed foroptimum performance in deep, powdery snow may render the ski lessversatile in various other snow conditions. Therefore, the advantage ofhaving the fin topside is that on ice or hard pack and even in slush, atopside fin does not interfere with the steering characteristics of theunderneath structures of the ski. However, the fin becomes functional indeeper snow and especially in deep, powdery snow, which is light andfluffy and which may not present much resistance to sideways slippage ofthe skis.

A single fin is sufficient to reduce sideways slippage so long as thefin is located on the topside of the ski substantially adjacent to theoutboard edge of the ski. Such a construction means that a snowmobilewill have a right and left ski with the right ski having its topside finalong its right edge and the left ski have its topside fin along itsleft edge. Where a tri-keel ski is employed, the fin may besubstantially a vertical extension of the outboard keel of such amulti-keel ski. The fin, of course, may have a vertical orientationwhich departs from a perpendicular orientation such that the fin may beflared outboard so that the top edge of the fin is farther outboard thanthe lower portion of the fin. The term “vertical,” as used herein,includes a perpendicular orientation as well as orientations whichdepart to some limited degree from perpendicular. The fin may have asail area which is substantially planar or the fin may be constructed sothat a curved surface is provided whereby the curve is verticallyoriented such that the top edge of the fin is curved to the outboardside of the ski. Such a curved vertical surface may continue to form anoverhanging lip. The fin, as desired, may be tilted inboard, however,its effectiveness is somewhat diminished except where an outwardlyprotruding lip is included.

While employment of a fin is particularly advantageous on the newer skissuch as the curved, plastic, multi-keeled skis, it should be understoodthat the invention of a ski with a topside fin to prevent lateralslippage during turns in deep powder snow also applies to metal skis andto skis having an essentially flat running surface with a single centralkeel whether it be a shallow or deep keel. The probability of sidewaysslippage during turns in deeper snow is a problem with almost everystructure and shape of snowmobile skis heretofore constructed orcurrently in use. A topside fin useful with a single keel ski mayrequire greater sail area than a fin used in conjunction with anoutboard keel.

The instant invention provides a significant improvement to all skis:flat skis, skis without an outboard keel, curved skis and multi-keelskis by inclusion of a substantially vertical topside fin, especiallyone having an outwardly curved lip. The topside fin is preferablylocated at the outboard margin of the ski with sufficient outer surfacearea to resist side slippage of the ski in a turn. As the snow isimpacted by the fin, the snow densifies and with the inward tilt of thefin during a turn because of the camber of the ski steering mechanism,the snow tends to flow upward along the outer surface of the fin. Suchupward flow of the snow will overflow the top of a flat vertical fin.However, a laterally projecting lip provided at the top of the finsignificantly minimizes this snow overflow, thereby maintaining thedensified snow against the fin, improving resistance to side slippage,while the upward movement of the snow exerts a lifting force on theoutwardly projecting lip, thereby providing better flotation of the ski,thus achieving a dual effect to improve performance of the ski in aturn.

Especially improved results are achieved with a multi-keeled ski,preferably a ski with a curved (convex) running surface and at least onetopside fin projecting substantially vertically upward, although it mayflare to the outboard. Such a fin is particularly effective whenstructured with an outwardly projecting lateral lip. The fin preferablyhas an irregular upper edge whereby the height of the fin is at itsmaximum approximately at the midpoint of the ski with a diminishingheight both fore and aft although the fin area aft of the midpoint maybe slightly greater than the area forward of the midpoint. Skis withdual fins with outwardly projecting lips are particularly effective.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention may be more fully described and understood by reference tothe drawings contained herein.

FIG. 1 is a perspective view of a tri-keel ski of the instant inventionillustrating a single, outboard, vertical, flat fin.

FIG. 2 is an elevational view of the ski on FIG. 1 in which a preferredprofile of the vertical fin is illustrated.

FIG. 3 is a lateral cross-sectional view along section line 3-3 of theski of FIG. 1 showing the overflow of snow over the top of the verticalfin of FIG. 1 during a turn.

FIG. 4 illustrates a ski having a vertical fin with a curved lipprojecting laterally outboard from the top of the fin.

FIG. 5 is a cross-sectional view of the ski in FIG. 4 along sectionlines 5-5.

FIG. 6 is a cross-sectional view of a ski with a vertical fin and anoutwardly projecting fin lip.

FIG. 7 is a cross-sectional view of the ski of FIG. 8 along sectionlines 7-7 with a pair of substantially vertical fins integral with atri-keel ski wherein the outer surface of the fin is substantially acontinuation of the outer surface of each outboard keel and having anoutwardly projecting curved lip along the upper edge of each fin.

FIG. 8 is an elevational view of a ski with a longitudinalarcuate-shaped fin and lip.

FIG. 9 is a bottom, plan view of the ski of FIG. 8.

FIG. 10 is a cross-sectional view of the ski of FIG. 9 along sectionlines 10-10.

FIG. 11 is a cross-sectional view of the ski of FIG. 9 along sectionlines 11-11.

FIG. 12 is a plan view of the top of a snowmobile ski with laterallyprojecting lips which have outer parabolic edges.

FIG. 13 is a cross-sectional view of the ski of FIG. 12 along sectionlines 13-13.

FIG. 14 is a mid-ski cross-sectional view of the ski of FIG. 12 alongsection lines 14-14.

FIG. 15 is a cross-sectional view of the ski of FIG. 12 along sectionlines 15-15.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view of a ski 10 of the instant inventionillustrating a single, outboard, vertical flat fin 11. The ski 10 ofFIG. 1 is a tri-keel structure with outboard keel 12 being shown.

FIG. 2 is an elevational view of the ski on FIG. 1 in which a preferredarcuate profile of the vertical fin 11 is illustrated. The forward area13 and the aft area 14 are substantially equal when measured from anapproximate midpoint of the fin 11. This midpoint is typically laterallyaligned with the attachment means of the ski 10 whereby the steering andsupport mechanism of the snowmobile is attached to the ski, i.e.,approximately the midpoint longitudinally of the ski running surface.While the ski of FIG. 2 is illustrated with a curved, convex runningsurface, an arcuate-shaped fin is also useful with a ski having anessentially flat running surface.

FIG. 3 is a lateral cross-sectional view of ski 10 along section lines3-3 of FIG. 2. This sectional view is illustrated at a titled angle suchas would be experienced by the ski during an inboard turn. The camber ofthe steering mechanism results in such a tilt. As can be seen from FIG.3, the outboard keel and the fin provide most of the effective sail areawhich minimize any side slip of the ski during an inboard turn. Asstated elsewhere herein, a dual fin ski is especially useful. While itis the outboard fin on the outboard ski which is most useful in turns inpreventing side slippage, the inboard fin on the inboard ski alsosignificantly assists in preventing side slippage and where the fins areprovided with outwardly projecting lips, all four fins with lips assistin providing improved flotation. In the description herein, the outboardski is the right ski in a left-hand turn while the left ski is theinboard ski in a left turn; and vice-versa during a right turn.

FIG. 3 illustrates the overflow of snow (curved line with arrow) overthe top of the fin during a turn, similar to the escape of wind from thesails of a sail boat when it lists drastically to leeward. While evenlight, powdery snow has greater density than air, when such powdery snowis in an agitated state, as occurs when it's disturbed by a snowmobileski cutting through it, the snow assumes a much lower density than whensitting in a settled state and its acts like a very low density fluid.This type of snow is frequently encountered after a snow storm in theWestern U.S. and Canada although it can be encountered anywhere that adry snow fall occurs. The term “dry” refers to snow which has fluffycrystals of low moisture content.

FIG. 4 is a perspective view similar to FIG. 1, however, the fin 11 hasah outwardly projecting lip 15 which is effective to prevent snowoverflow of the fin (see FIG. 5) as well as to act as a foil, e.g.,similar to an air foil, to provide some additional flotation. The lip isintegral with the top edge of the fin and is spaced vertically from thetop of the ski and is thus well removed from the surface of the snowexcept when the ski is running in deep, light, powdery snow.

The lip 15 preferably has substantially the same cross-sectional shapeand dimension over its length although it may gradually emerge from thefin near its front to a maximum width near the midpoint of the fin andthen gradually merge with the fin near its rear. The area of the lip isas important generally as its length. Typically, the lip 15 has a lengthwhich is at least about 20% of the length of the upper edge of the fin11. Fin 11 has a generally arcuate shaped upper edge, as illustrated inFIG. 2, although for skis with a substantially curved (convex) runningsurface, the upper edge of the ski may be linear since the curve of theski will provide a maximum height of fin 11 near its midpoint. Alaterally projecting lip attached to a fin with a substantially linearupper edge is effective for minimizing overflow of snow over the fin,but a lip which is substantially linear over its length generallyprovides less flotation than a lip with an arcuate shape along itslength.

A flat-faced fin is very useful in minimizing side-slipping of turnedsnowmobile skis. However, a ski as shown in a lateral cross-section inFIG. 5 which has a fin with an outwardly projecting lip 15 which isover-curved, i.e., forms an enclosed arch, traps the upward flow of snowalong the vertical fin to significantly increase the effectiveness ofthe fin. The lip has at least part of its lower or underneath surface atan angle of about 90° to the substantially planar surface of the outerfin surface. The lip curves downward along its outermost edge so thatpart of the lower lip surface is substantially parallel to the outersurface of the fin. As the fin presses against the snow during a turn,it tends to densify the snow so that the upward flow of snow may have agreater density than it would otherwise have, so that the upward forceon the projecting lip may provide increased flotation. The skiillustrated in FIG. 5 has a curved lip which is generally preferred inminimizing overflow of snow along the fin and to provide some flotationeffect.

The camber of the steering causes a tilt of about 4 to about 8°depending upon the severity of the turn. The maximum camber occurs whenthe steering is at its innermost locked position.

FIG. 6 is similar to FIG. 5 except that lip 15 is alaterally-projecting, substantially planar lip. Such a lip is effectivewith a fin which has either preferred arcuate upper edge or a linearupper edge. In both FIGS. 5 and 6, the laterally directed arrows showthe possible sideways slip of the skis while the upwardly directedarrows show the snow resistance caused by the fin and the trapping ofthe snow under the lip, preventing snow overflow and providingadditional flotation. As shown in FIG. 6, the fin 11 may exhibit asubstantially vertical orientation (or, more specifically, substantiallyperpendicular to the upper surface of the ski) or it may exhibit anoutward slant, as shown by dashed lines, of up to, for example, 25°.

FIG. 7 is a cross-sectional lateral view of a ski showing a pair ofupstanding fins along each outer edge of the ski wherein each finproceeds vertically at a slight outward flare for a distance and thenhas an arched lip which curves out perpendicularly from the fin and thencurves slightly downward to terminate along its outermost edge. Thedotted lines show a lip which is over-curved so that a portion of itsinterior surface 16 is substantially parallel to the outer surface ofthe fin. This particular arched structure has a lip which is definedherein as an over-curved lip that may include substantially a halfcircle. It is a particularly useful shape inasmuch as when the ski istilted as shown in FIG. 5 and snow at the outboard edge of the ski issweeping up along the fin as the fin is pushing in the lateral directionthe arched lip very effectively captures the upwardly moving snow andprevents it from spilling over the top of the fin. This arched liphaving a longitudinally arcuate shape also is effective in providingimproved flotation under substantially all operations in deep snow incomparison to a laterally projecting planar lip.

As noted above, a snowmobile ski fitted with a single fin, for example,as shown in FIG. 1, may be particularly useful even where the fin islocated along only one edge of the ski so long as that edge is theoutward edge of the ski. Skis of this type would be of a left and rightvariety with the right-hand ski having its fin along its right edge whenviewed from the rear of the ski and the left-hand ski having the finalong its left edge when viewed from the rear of the ski. Fins on theinterior edges of the ski are less effective because the fin has verylittle to do since the outboard fin functions to do most of the work ina turn. An inboard fin on the inboard ski is effective so that skis withdual fins are especially useful.

The fins to be optimally effective have a maximum sail area. This sailarea being defined herein as the area of the fin which resists lateralmotion in deep powdery snow. A larger sail area may be required wherethe fin does not have an upper outwardly projecting lip. Also, a largersail area may be required for a ski without an outboard keel to achievea desired level of resistance to side slippage. For a conventional skihaving a length of about 35 inches to about 45 inches, a fin with a sailarea of about 25 square inches to about 50 square inches enhances thecontrol of a snowmobile in deeper snow and minimizes substantially thelateral slippage or sideways slippage of the skis during turns in deepsnow without causing excessive drag in deep, powdery snow or interferingwith ski performance in slush or on hard pack or icy conditions.

Fins included on a ski with an outboard keel may have less sail areainasmuch as the outboard keel provides some resistance to side slippage.

While some older skis have previously been designed with some structureson top of the ski, the topside structures have been generally includedfor the purpose of strength, rigidity or aesthetics. Such priorstructures have been included also for providing attachment means forattaching the steering mechanism of the snowmobile to the ski. Also,typically these topside structures have been spaced to the inboard fromthe outer edge of the skis and have not been either structurallyengineered or positioned to provide any significant resistance tolateral slippage of the skis during a turn. The more inboard anupstanding structure is the less exposed it is to snow during a turninasmuch as the tilt of the ski raises the outboard edge of the ski suchthat any topside inboard structure is essentially shielded from impactwith the snow. For example, in U.S. Design Pat. 366,014 a pair of ridgesis located topside of the ski extending from the tip of the ski to aposition somewhat adjacent the rear of the ski. These ridges appear tobe substantially the same height and appear to have a curvedcross-section such that the ridges are there either for aestheticpurposes or to provide some rigidity. The ridges do not appear to bestructured or designed to preclude any resistance to lateral slippage ofsuch a ski in a turn.

The topside preferred location of a fin for the purpose of minimizingside slippage in turns is at the very lateral edge of the ski, althoughit may be slightly inboard of the ski edge if the fin has significantheight and area or is tilted outwardly so that a significant portion ofthe fin is aligned with or is outboard of the outer edge of the ski.Recessing the fin even a slight distance inboard of the outer edge tendsto diminish the effectiveness of a fin even one having an outward tilt.This slight diminishment may, however, be tolerable for multipurposeskis where the upturned tip of the ski substantially protects orprevents snow contacting such a fin during straight ahead running.

Preferred fin structures for skis of the instance invention are oneswhich are longitudinally straight with the longitudinal axis of the finbeing substantially parallel to the longitudinal axis of the ski. Finswith a slight longitudinally arcuate shape, when viewed from above, maybe useful so long as a substantial portion of the fin is along the outeredge of the ski, especially that portion of the fin near thelongitudinal midpoint of the ski. Further, as noted hereinabove, anoutwardly projecting lip featured along the upper edge of a topside finsignificantly improves the effectiveness of the fin in preventing sideslippage and improving snow flotation in both turns and during straightahead running in deep, powdery snow.

The ski construction which is most versatile and especially effective inboth light and heavy deep snow is that shown in an elevational view inFIG. 8. The overturned lip 15 preferably extends essentially the wholelength of an upright fin. The preferred fin shape is that illustrated inFIG. 7, which is a mid-ski cross-sectional view along section lines 7-7of FIG. 8, where its upper edge has an arcuate shape, i.e., an inverserocker shape. This inverse rocker shape and the projecting, overturned(arched) lip 15 provides excellent flotation (lift) when runningstraight in deep snow and for maintaining excellent control in allturns.

While a lip of substantially any size and shape which projects outwardlyfrom the upper edge of an upright fin provides some effectivenessagainst snow overflow, an arched lip having a substantial length isgenerally preferred. Such an arched lip may merge into the fin at themost forward point of the lip, preferably near the front terminus of thefin, which is preferably near the base of upturned tip of the ski. Thearched lip may have approximately the same lateral shape and lateraldimension over its entire length. The rear terminus of the lip may ormay not merge into the fin. A preferred lip structure for the lip is onewhere the lip transitions from an arched structure to an essentiallyplanar structure at each terminus of the lip so that the lower surfaceof the lip essentially merges with and becomes part of the lower runningsurface of the ski where each merge occurs.

Skis which are substantially symmetrical in cross-section are generallypreferred, i.e., an identical fin and outwardly projecting lip isprovided along each lateral edge of the ski, as illustrated in FIG. 7.Also, it is generally preferred that the ski be one which is a tri-keelor dual keel ski wherein rocker shaped keels are along the lateral edgesof the ski and that the fin is essentially an upward projection whichcontinues the outer surface of each outer keel in an upward direction.

It is generally preferred that the fin sail area is at least equal tothe outboard surface area of an outer keel of the snowmobile ski andthat the enclosed surface area of the arched lip is at least equal tothe sail area of said fin. The lowest portion of the arched lip istypically near the forward portion of the fin. Generally, it ispreferred that the lowest portion of the lip be sufficiently above therunning surface of the ski so that it does not contact harder packedsnow during running straight ahead or in turns or the lip transitions inshape to merge with or become part of the lower running surface of theski at the fore end aft portion of a lip. Thus, a preferred lip iscurved or curvilinear along the length of the upper edge and islaterally arched or curved with the interior surface of such arched lipfacing downward.

As may be seen from FIG. 9, a plan view of the bottom of a ski havingdual fins with outwardly projecting lips 15, the outer edges of the twolips 15 are substantially parallel to one another. Such a ski has asubstantially uniform width when measured from the outer edge of one lipto the outer edge of the other lip. Each lip also has a substantiallyuniform width over its entire length. Each lip substantially merges intothe ski tip (see FIG. 10, a cross-sectional view along section lines10-10 of FIG. 9) so that the ski tip at the region of such lip merger issubstantially the same width as the width of the ski when measured fromthe outer edge of one lip to the outer edge of the other lip at anypoint along the length of the lips.

Further, as illustrated in FIGS. 9 and 10, the merger of the lips foreand aft may merge into the running surface off the ski so that the lipcontact with deep snow provides a gradual contact at the front end and agradual departure at the rear of the ski. The merging of lips 15 at therear of the ski into the lower running surface helps to keep the ski ina better planing position. If such rear merger is not incorporated intoa ski with outwardly projecting raised lips, such skis will tend to havethe tip of the ski riding higher than desired for good planing when theski is running forward in deep snow.

Another feature of the ski illustrated in FIG. 9 is that the runningsurface of the ski which contacts hard pack snow is a substantiallyuniform width over substantially its entire length and is substantiallysymmetrical about a longitudinal axis of the ski.

Certain embodiments of the invention provide an improved snowmobile skifor running on different snow conditions in which the ski has a lowerrunning surface structured and adapted for running on hard pack and/oricy surfaces and a raised running surface which is at least partiallyelevated and outboard, especially its mid-ski portion, from said lowerrunning surface. The raised running surface is preferably connected orjoined to the ski by a fin 11 or web member which is preferably at leastpartially substantially vertical and is preferably substantiallycontiguous in length with the raised running surface.

Such a ski is preferably a unitary ski, although an existing ski couldbe retrofitted with a fin 11 having a projecting outboard lip 15. Thefin 11 and outboard lip 15, if made of metal, could be riveted or weldedto a metal ski, or an integral fin and lip structure made of plasticcould be fixed to a plastic ski by screws or a structurally strong glue,such as an epoxy. Generally, however, a unitary ski is provided byappropriate manufacturing techniques. A ski can readily be made ofplastic as a one-piece construction by hot-forming a sheet ofthermoplastic material or by casting either a thermoplastic orthermosetting resinous material in an appropriately shaped mold.

Skis of the type described in the immediately preceding paragraphs arepreferably symmetrical about a vertical plane passing through thelongitudinal axis of the ski. One such type of ski is illustrated inFIGS. 7, 9, 10 and 11. By comparing cross-sectional views 7, 10 and 11,which are cross-sectional views at mid-ski portion (FIG. 7) forward andaft position (FIG. 10) and quarter ski position (FIG. 11), the gradualdevelopment of a raised running surface can be seen. The gradual changein shape from a deep arched configuration (FIG. 7) to a slightly lessarched configuration (FIG. 11) to a merged shape is a generallypreferred configuration. Also, as can be seen from FIGS. 8 and 9 andfrom cross-sectional views 7, 10 and 11, the outer keels 12 areillustrated as being shorter and less deep than those generally utilizedon skis without an elevated running surface while still retaining goodrunning and steering performances in all types of snow conditions.

An unique ski structure is shown in FIGS. 12, 13, 14 and 15, whereinFIG. 12 is a plan view of the top of a ski having parabolic lateral lipedges. While a parabolic snowmobile ski has certain performancecharacteristics without an upper or raised running surface, the ski inFIG. 12 has parabolic shaped outer edge of the outwardly projecting lipof the ski. The outer longitudinal edge of the lip 15 follows aparabolic contour such that the width between opposed lateral edges ofthe outwardly projecting lips is less at the waist of the ski, i.e.,central region, than at the fore or aft portions of the ski. The lateraledges of the running surface of the ski are essentially straight andparallel to one another, which is also true of the keels, whether one,two or three keels are utilized. Thus, the lower running surface may beconventional, e.g., such as the running surfaces illustrated in U.S.Pat. Nos. 5,700,020, 6,012,728 and 6,267,342 to Noble.

The parabolic shape of the upper running surface lateral edges contactsthe snow only when deep snow is encountered whereby the parabolic shapeassists the skis in effectively turning since the camber built into thesteering mechanism to tilt, thereby dipping the inboard edge of the lipinto the snow, causing the ski to tend to carve a turn along thecurvature built into the edge of the inboard lip.

The curvature built into the lateral edges of the elevated lips isrelatively minimal, the curvature realizing a depression of aboutone-quarter to about one inch from an imaginary straight line connectingthe maximum projection both fore and aft of the lip 15 as illustrated inFIG. 12 at a-a.

This curvature may also be an arc, i.e., portion of a circle, about aradius of about 20 to about 60 inches, although radii intermediate ofthose lengths are preferred.

The inward tilt of the fins 11 to create a parabolic shape with lips 15of uniform widths over their length can create a molding challenge,however, the use of a mold having at least three segments can besuccessfully used. Also, the ski can be made with the fin substantiallyvertical by thermoforming of a thermoplastic sheet, then putting the skiin a hot press to urge the two opposed fins towards one another to causethe desired shape to occur.

While a ski with parabolic edges on the upper raised running surface hascertain advantages, it is also within the scope of the invention to havea ski with an inwardly tilted fin with the raised running surface havingparallel outer edges. This is accomplished by having a uniform inwardtilt of the fin with a lip, for example, of a uniform width, or in theinstance of a fin having a greater inward tilt at its midportion than ateither end, then a lip which increases gradually in width from each endtowards the center can provide a straight, linear edge whereby the outeredges of the raised running surface are parallel to one another andparallel to the outer edges of the lower running surface.

An inward tilt of the fin equivalent to a typical camber of a steeringmechanism is preferred, however, inward fin tilts less than about 5° andinward fin tilts greater than about 8° may also find utility for certainpurposes and snow conditions.

Although the instant invention has various useful embodiments, theinvention is not intended to be limited by the above description orattached illustrations but to include all embodiments and variations asset forth in the attached claims.

1. A snowmobile ski comprising: a body having an intended runningsurface, a second, opposing surface, a first longitudinally extendingedge and a second longitudinally extending edge; first lip extendinglaterally outwardly relative the first edge of the body, the first liphaving a first edge and a second edge, wherein both the first edge andsecond edge of the first lip are vertically displaced from the second,opposing surface of the body at a location that is approximately at alongitudinal midpoint of the ski.
 2. The snowmobile ski of claim 1,wherein at least a portion of the first lip exhibits an arcuate profilealong a longitudinal length thereof.
 3. The snowmobile ski of claim 1,further comprising a second lip extending laterally outwardly relativethe second edge of the body.
 4. The snowmobile ski of claim 3, whereinthe second lip includes a first edge and a second edge, wherein both thefirst edge and second edge of the second lip are vertically displacedfrom the second, opposing surface of the body at a location that isapproximately at the longitudinal midpoint of the ski.
 5. The snowmobileski of claim 1, further comprising at least one keel member protrudingfrom the intended running surface.
 6. The snowmobile ski of claim 5,wherein the at least one keel member includes a first keel membersubstantially laterally centered on the intended running surface.
 7. Thesnowmobile ski of claim 6, wherein the at least one keel member furtherincludes a second keel member laterally positioned adjacent the firstedge of the body and a third keel member laterally positioned adjacentthe second edge of the body.
 8. The snowmobile ski of claim 1, whereinthe first lip exhibits a variable width.
 9. The snowmobile ski of claim8, wherein the first lip exhibits a maximum width at a locationproximate the midpoint of the ski.
 10. The snowmobile ski of claim 1,wherein the first lip gradually merges into the second, opposing surfaceof the body in an intended forward direction.
 11. The snowmobile ski ofclaim 1, wherein the first lip exhibits a substantially constant widthover substantially its entire length.
 12. The snowmobile ski of claim 1,wherein the first lip exhibits a substantially concave lower surface.13. The snowmobile ski of claim 1, further comprising at least onesubstantially upright fin extending between the first edge of the bodyand the first edge of the lip.
 14. The snowmobile ski of claim 13,wherein the lip extends over at least about 40% of a length of an upperedge of the at least one fin.
 15. The snowmobile ski of claim 13,wherein a surface of the at least one fin disposed between the firstedge of the body and the first edge of the lip exhibits an area of about25 square inches to about 50 square inches.
 16. The snowmobile ski ofclaim 13, wherein the at least one fin exhibits a maximum height ofabout four inches.
 17. The snowmobile ski of claim 13, wherein a heightof the at least one fin diminishes from a maximum height near thelongitudinal midpoint of the ski to a minimum height proximate to both afore and an aft termini of the at least one fin.
 18. The snowmobile skiof claim 13, wherein the at least one fin gradually diminishes in heightin both fore and aft directions to termini that are less than about oneinch in height.
 19. The snowmobile ski of claim 18, wherein the terminisubstantially merge into the second, opposing surface of the ski. 20.The snowmobile ski of claim 13, wherein the intended running surfaceexhibits a substantially convex geometry along its length.
 21. Thesnowmobile ski of claim 13, wherein the at least one fin is integrallyformed with the body.